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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Split-film anemometer measurements on an airfoil with turbulent separated flow

Experimental studies of turbulent separation on airfoils have been conducted to aid in improving theoretical models of post-stall airfoil behavior. The studies utilize a variety of pressure and hot-film probes. The split-film anemometer has proved particularly valuable for measurement of highly turbulent reversing flows. Suggested techniques for on-line digital computer processing of the data are discussed.

Wentz, W. H., Jr.↗
NASA NTRS1979

A split sphere 60,000 ton press

A split sphere press which can have a total force of 60,000 tons applied to its exterior by a 0.55 GPa hydrostatic pressure vessel is described. The inner anvils are made of tungsten carbide and show considerable plastic deformation under load. Much greater pressures, in the 100 GPa range, are possible if diamond tipped anvils are used. Because of the uniformly loaded multi-anvil arrangement, the diamond tips can be maintained under a high degree of compressive load and therefore prevent fracture which may occur in a conventional opposed anvil arrangement. Press operation on CdS, ZnSe, ZnS, GaP, and BP samples is described, and their resistance versus external pressure on the sphere are plotted.

Wanagel, J.↗
NASA NTRS1979

Application of a velocity-split Navier-Stokes solution technique to external flow problems

A method for solving the Navier-Stokes equations based on splitting the velocity vector into its rotational and irrotational parts has recently been applied successfully to internal flow computations. In this paper, the applicability of the method to external flows is examined by studying two model problems; laminar incompressible flow over semiinfinite and finite flat plates. For these problems the procedure accurately reproduces the known solutions and is computationally very efficient even at high Reynolds numbers. Computational aspects of the method are discussed along with the possibility of using the procedure to retrofit a viscous capability into existing transonic potential flow codes.

Dwoyer, D. L.↗
NASA NTRS1980

Velocity-split Navier-Stokes solution procedure for incompressible high Reynolds number external flows

A method for solving the Navier-Stokes equations based on splitting the velocity vector into its rotational and irrotational parts was sucessfully applied to internal flow computations. The applicability of the method to external flows is examined by studying several model problems. The model problems are those of laminar and turbulent incompressible flow past a semi-infinite flat plate and laminar incompressible flow past a finite flat plate. For these problems, the procedure accurately reproduces the known solutions and is computationally very efficient even at high Reynolds numbers. Computational aspects of the method are discussed along with the possibility of using the procedure to retrofit a viscous capability into existing potential flow codes.

Dwoyer, D. L.↗
NASA NTRS1980

Studies of thermochemical water-splitting cycles

Higher temperatures and more isothermal heat profiles of solar heat sources are developed. The metal oxide metal sulfate class of cycles were suited for solar heat sources. Electrochemical oxidation of SO2 and thermochemical reactions are presented. Electrolytic oxidation of sulfur dioxide in dilute sulfuric acid solutions were appropriate for metal oxide metal sulfate cycles. The cell voltage at workable current densities required for the oxidation of SO2 was critical to the efficient operation of any metal oxide metal sulfate cycle. A sulfur dioxide depolarized electrolysis cell for the splitting of water via optimization of the anode reaction is discussed. Sulfuric acid concentrations of 30 to 35 weight percent are preferred. Platinized platinum or smooth platinum gave the best anode kinetics at a given potential of the five materials examined.

Remick, R. J.↗
NASA NTRS1980

A simple stripline design for uneven power split

A technique for the design of stripline or microstrip power dividers for unequal, but in-phase, power split is described. The output power ratio is determined by selecting the location of the input port in a manner analogous to the tap point for an electric power transformer. The technique yields a usable bandwidth of 7 to 8 percent and is attractive for tapered amplitude distribution networks for narrow band phased arrays.

Bailey, M. C.↗
NASA NTRS1980

An ab initio calculation of the zero-field splitting parameters of the 3A-double prime state of formaldehyde

The spin dipole-dipole and spin-orbit contributions to the zero-field splitting of the 3A-double prime state of formaldehyde have been evaluated at the excited state experimental geometry. Ab initio CI wave functions were generated from a Dunning double zeta plus polarization bases set using 3A-double prime rhf orbitals. Twelve states of each symmetry were used to evaluate the second-order spin-orbit effect. The resulting values of D and E were 0.19 and 0.03 kayser with the principal magnetic axes rotated 36 deg from the CO bond. The values of alpha and beta relative to the inertial axes were calculated to be 0.03 and 0.01 kayser compared to the experimental values of 0.05 plus or minus 0.01 and 0.02 plus or minus 0.02 kayser.

Davidson, E. R.↗
NASA NTRS1980

A hybrid water-splitting cycle using copper sulfate and mixed copper oxides

The Institute of Gas Technology has derived and developed a hybrid thermochemical water-splitting cycle based on mixed copper oxides and copper sulfate. Similar to other metal oxide-metal sulfate cycles that use a metal oxide to 'concentrate' electrolytically produced sulfuric acid, this cycle offers the advantage of producing oxygen (to be vented) and sulfur dioxide (to be recycled) in separate steps, thereby eliminating the need of another step to separate these gases. The conceptual process flow-sheet efficiency of the cycle promises to exceed 50%. It has been completely demonstrated in the laboratory with recycled materials. Research in the electrochemical oxidation of sulfur dioxide to produce sulfuric acid and hydrogen performed at IGT indicates that the cell performance goals of 200 mA/sq cm at 0.5 V will be attainable using relatively inexpensive electrode materials.

Schreiber, J. D.↗
NASA NTRS1980

Direct thermal water splitting by concentrated solar radiation for hydrogen production. Phase O: Proof of concept experiment

The direct production of hydrogen from water and solar energy concentrated into a high temperature aperture is described. A solar powered reactor able to dissociate water vapor and to separate the reaction product at high temperature was developed, and direct water splitting has been achieved in a laboratory reactor. Water vapor and radiative heating from a carbon dioxide laser are fed into the reactor, and water vapor enriched in hydrogen and water vapor enriched in oxygen are produced. The enriched water vapors are separated through a separation membrane, a small disc of zirconium dioxide heated to a range of 1800 k to 2800 k. To avoid water vapor condensation within the reactor, the total pressure within the reactor was limited to 0.15 torr. A few modifications would enable the reactor to be operated at an increased pressure of a few torrs. More substantial modifications would allow for a reaction pressure of 0.1 atmosphere.

Genequand, P.↗
NASA NTRS1981

A preliminary study of relaxation methods for the inviscid conservative gasdynamics equations using flux splitting

Plus minus flux vector split schemes are combined with the multigrid relaxation method to obtain fast rates of iterative (or steady state) convergence. On model nonlifting biconvex airfoil flow, steady state convergence is obtained using multigrid in 40 iteractions for subsonic cases and in 120 iterations for transonic cases. A 65 x 33 stretched grid is used. However, the multigrid scheme used here (and there are numerous variations) sometimes could not be made to work for transonic cases with a large number of supersonic points. Moreover, the multigrid method is only several times faster than the conventional algorithm which itself could perhaps be accelerated by other means. Nethertheless, with proper adjustment the multigrid method will ultimately lead to very fast rates of iterative convergence.

Steger, J. L.↗
NASA NTRS1980

Nonrelativistic hyperfine splitting in muonic helium by adiabatic perturbation theory

Huang and Hughes have discussed the hyperfine splitting delta mu of muonic helium using a variational approach. In this paper, the Born-Oppenheimer approximation is used to simplify the evaluation of delta mu in the nonrelativistic limit. The first-order perturbed wave function of the electron is obtained in closed form by modifying the method used by Dalgarno and Lynn. The result is close to those of Huang and Hughes which required a large Hylleraas expansion and considerable extrapolation.

Drachman, R. J.↗
NASA NTRS1981

A split explicit reformulation of the regional numerical weather prediction model of the Japan Meteorological Agency

The split explicit integration scheme for numerical weather prediction models is employed in a version of the regional numerical weather prediction model of the Japan Meteorological Agency. The finite-difference scheme of the model is designed in the manner proposed by Okamura (1975). The horizontal advection terms in the governing equations are integrated with a time step limited by the wind speed while the terms which describe inertial-gravity oscillations are integrated in a succession of shorter time steps. The physical processes included within the model are precipitation, small-scale convection, surface exchanges of sensible and latent heat, and radiative heating and cooling. An example of a surface pressure forecast over Europe is shown for initial data observed at 0000 GMT 29 December 1979. Quantitative precipitation forecasts over Europe and North America for the 24 h period beginning at 0000 GMT 30 December 1979 are also shown. It is concluded that the model is capable of realistically depicting the evolution of synoptic-scale systems.

Duffy, D. G.↗
NASA NTRS1982

Split Coil Forms for Rotary Transformers

Split cores for rotor and stator windings of rotary transformer mounted around their respective coils (which are in bobbins) and cemented together. This arrangement simplifies winding of stator coil to go in a slot in inner diameter of stator coil. One practical application of rotary transformers fabricated according to this technique is for centrifuges, in which conventional sliprings are of uncertain reliability.

Mclyman, C. W. T.↗
NASA NTRS1982

Low-level water vapor fields from the VISSR atmospheric sounder (VAS) split window channels at 11 and 12 microns

A series of high-resolution water vapor fields were derived from the 11 and 12 micron channels of the VISSR Atmospheric Sounder (VAS) on GOES-5. The low-level tropospheric moisture content was separated from the surface and atmospheric radiances by using the differential adsorption across the 'split window' along with the average air temperature from imbedded radiosondes. Fields of precipitable water are presented in a time sequence of five false color images taken over the United States at 3-hour intervals. Vivid subsynoptic and mesoscale patterns evolve at 15 km horizontal resolution over the 12-hour observing period. Convective cloud formations develop from several areas of enhanced low-level water vapor, especially where the vertical water vapor gradient relatively strong. Independent verification at radiosonde sites indicates fairly good absolute accuracy, and the spatial and temporal continuity of the water vapor features indicates very good relative accuracy. Residual errors are dominated by radiometer noise and unresolved clouds.

Chesters, D.↗
NASA NTRS1982

Solution of the two-dimensional Euler equations with generalized coordinate transformation using flux vector splitting

An implicit finite difference code using flux vector splitting has been developed for solving the two-dimensional inviscid gas dynamics equations. The method is spatially second-order acurate, fully conservative, and uses body-conforming generalized coordinates for treating complex geometries. Numerical results have been obtained for transonic flow over a circular cylinder and airfoils. Steady results for a half cylinder (top and bottom symmetry-imposed) range from critical flow to a strong shock case with rotationally induced flow separation. Full cylinder solutions at freestream Mach number values of 0.5, however, show unsteady oscillation. A perturbation form of the method has also been developed and used to compute both fore and aft inviscid flow separation about a cylinder for a nonuniform incoming stream.

Buning, P. G.↗
NASA NTRS1983

A split delta-V technique for drift control of geosynchronous spacecraft

A split-delta-V technique is presented for the east-west stationkeeping of geosynchronous spacecraft using the linearized optimal transfer strategies for near-circular coplanar orbits. The maneuvers are carried out by taking advantage of the dynamics of the spacecraft in order to cancel out the effect of the drift accumulated between successive impulsive delta-V's. A stability analysis is then carried out in order to determine the effect of implementing a series of precanned maneuvers at the end of each drift cycle in an autonomous mode by taking into account initial orbit determination uncertainties and execution errors emanating from each delta-V. It is shown that small tolerance deadbands are violated after only a few cycles and the system is unstable.

Kechichian, F. A.↗
NASA NTRS1983

Low level water vapor fields from the VISSR Atmospheric Sounder (VAS) 'split window' channels

The use of the 11 and 12-micron IR-radiometer channels of the VISSR Atmosphere Sounder (VAS) on the GOES to detect water vapor in the lowest 300-400 mb of the troposphere is reported. An algorithm is developed to eliminate the background temperature, allowing the calculation of precipitable water (PW) over both land and water via a single-layer radiative model. This 'split-window' method is demonstrated in a case study, covering the US on July 13, 1981. PW values were calculated from five VAS images and compared with those from radiosonde data and surface measurements. It is shown that the VAS PW images have good resolution (15 km), reveal vivid, continuously evolving details, and differentiate deep, convection-supporting layers from shallow ones. PW ranged from 1.7 to 5.5 g/sq cm (+ or - 1.0 g/sq cm), in good agreement with other measurements. Since this method can detect mesoscale water-vapor fields in relatively clear air, it is considered of great potential value for numerical forecasting.

Robinson, W. D.↗